1. Field of the Invention
The invention relates to ball drop injection assemblies for use at a wellsite during hydraulic fracturing operations.
2. Description of the Related Art
Frac ball injection to control fluid flow in a well has seen use in fracturing operations for some time. Frac balls are often inserted into a wellbore to control fluid flow between different sections of a well. The balls are pumped downhole along with well stimulation fluid. It has generally been determined to be time consuming and potentially hazardous for on-site personnel to manually handle frac balls around the wellbore as equipment sometimes extend high into the air and a number of high pressure lines can surround the well to pump stimulation or other fluids into the well. The industry has sought ways to limit the manual interaction required by on-site personnel when injecting frac balls at the wellbore. One option that reduces overall injection times and the amount of manual involvement by on-site personnel involves the use of frac ball dropping assemblies.
Frac ball dropping assemblies have seen greater use in fracturing operations more recently given the efficiencies that can be achieved with frac ball injection, and the additional safety factor they provide to on-site personnel. In fracturing operations it is useful to drop frac balls of varying sizes into the wellbore, where they can be pumped downhole. The frac balls can be used to control fluid flow beneath the surface in a well. This can be useful when, for example, it is more efficient to stimulate and produce from different stages of a well at a particular time in the overall fracturing operation. Over time hydraulic fracturing has seen greater use of ball drop assemblies to stimulate well production, in part because of the time savings and in part because of the reduced manual interaction required of on-site personnel.
Ball drop assemblies can require frac balls of sequentially larger diameter to be stored in a frac ball stack above the wellhead. The balls in this stack are often stored in water or other fluids and often require some degree of temperature control. Recently, dissolvable frac balls have seen increased use, dissolvable ball designs hold up better in dry and non-pressurized storage rather than in fluid and at wellbore pressure. It would be desirable to provide a dry and atmospheric pressure storage option for frac balls just prior to well injection. It would also be desirable to eliminate the need for temperature control of the ball drop apparatus.
In addition, ball drop assemblies have seen issues and often cannot function with balls of similar or substantially similar sizes coming one after another without substantially increasing the height of the ball drop assembly and adding additional structure to accommodate the configuration. Thus, it would also be desirable to provide a system that can handle the injection of substantially similar ball sizes in a sequential manner without the need to increase the height of the ball drop assembly.